The present disclosure is related to optical processing elements and, in particular, methods of manufacturing or fabricating an integrated computational element for use in an optical computing device.
Optical computing devices, also commonly referred to as “opticoanalytical devices,” can be used to analyze and monitor a sample substance in real time. Such optical computing devices will often employ a light source that emits electromagnetic radiation that reflects from or is transmitted through the sample and optically interacts with an optical processing element to determine quantitative and/or qualitative values of one or more physical or chemical properties of the substance being analyzed. The optical processing element may be, for example, an integrated computational element (ICE). One type of an ICE is an optical thin film interference device, also known as a multivariate optical element (MOE). Each ICE can be designed to operate over a continuum of wavelengths in the electromagnetic spectrum from the UV to mid-infrared (MIR) ranges, or any sub-set of that region. Electromagnetic radiation that optically interacts with the sample substance is changed and processed by the ICE so as to be measured by a detector. The output of the detector can be correlated to a physical or chemical property of the substance being analyzed.
An ICE (hereafter “ICE core”) typically includes a plurality of optical thin film layers consisting of various materials whose index of refraction and size (e.g., thickness) may vary between each layer. An ICE core design refers to the substrate, the number and thickness of the respective layers, and the refractive indices of each layer of the ICE core. The layers may be strategically deposited and sized so as to selectively pass predetermined fractions of electromagnetic radiation at different wavelengths configured to substantially mimic a regression vector corresponding to a particular physical or chemical property of interest of a substance of interest. Accordingly, an ICE core design will exhibit a transmission function that is weighted with respect to wavelength. As a result, the output light intensity from the ICE core conveyed to the detector may be related to the physical or chemical property of interest for the substance.